1. Field of the Invention
The present invention relates to an in-plane switching type of an active matrix type of a liquid crystal display apparatus for executing a display by rotating a liquid crystal molecule through an electric field generated parallel to a surface of a substrate.
2. Description of the Related Art
In a display panel of an in-plane switching (IPS) type of a liquid crystal display apparatus, its feature lies in a mechanism that can attain a wide field angle by putting liquid crystals at a predetermined interval between a pair of transparent substrates, and applying an effectively parallel electric field to the substrates and then rotating molecules of the liquid crystals in a direction horizontal to the inner surface of the substrate. The electric field parallel to the substrate is generated by placing a pixel electrode and a common electrode on one of the pair of transparent substrates for putting the liquid crystals between them, at a predetermined interval in a form of comb. On the other hand, in the comb electrode, the liquid crystals are raised in a direction vertical to the surface of the substrate. Thus, if the comb electrode is constituted by a transparent electrode such as ITO and the like, this constitution results in a problem of a drop in contrast and the like. So, it is necessary that the comb electrode is constituted by using an opaque electrode.
In the IPS type liquid crystal display apparatus, the technique for protecting the drop in brightness and the deterioration in contrast and field angle property is disclosed in, for example, Japanese Laid Open Patent Application (JP-A-Heisei, 9-269508).
Here, the configuration of the display cell in the conventional IPS liquid crystal display apparatus is described with reference to the drawings. FIG. 1 shows a first plan view (a side of a TFT substrate) according to the conventional display cell. A display cell 201 shown in FIG. 1 has an amorphous silicon 1, a pixel electrode 2, a gate electrode 3, a common electrode 4, a data line 5, a source electrode 6 and a drain electrode 7. Orientation films 11 are printed on the thus-created TFT substrate and respective color filters, each containing a color layer for coloration of equi-process, by using a method such as offset-print and the like. In the thus-created orientation film of the TFT substrate and the color filter substrate, the molecules of the orientation films are aligned in a predetermined direction by using a rubbing method (rubbing direction 19). Then, the cell gap material is put between the two substrates so that a predetermined interval is established between them, and they are combined in this way. Then, the liquid crystal is filled in the gap.
On the liquid crystal panel created as mentioned above, the full color display from a black display to a white display can be carried out by laminating the polarization plates, in which transmission axes are orthogonal to each other in a liquid crystal orientation direction defined by using the rubbing method, and freely applying a potential difference between the pixel electrode 2 and the common electrode 4.
The configuration of the display cell 201 will be described below. FIG. 2 is a section view taken on the line A-Axe2x80x2 of the cell 201. In FIG. 2, the upper structure located on an upper portion of a liquid crystal layer in which a liquid crystal 20 is placed is provided with a polarization plate 17, a conductive layer 16, a second transparent substrate 14, a black matrix 12, a color layer (color filter) 13, a smoothing film 15 and an orientation film 11. An edge (not shown) of the black matrix 12 is placed on the common electrode 4.
In FIG. 2, the lower structure located on the lower portion of the liquid crystal layer is provided with an orientation film 11, a passivation film 22, a data line 5, a pixel electrode 2, a layer-to-layer insulation film (gate insulation film) 10, a common electrode 4, a first transparent substrate 9 and a polarization plate 18.
Also, a mutual interval between the common electrode 4 and the pixel electrode 2 to generate an electric field in an effectively lateral direction to the substrate is set at about 10 xcexcm.
The polarization plates 17, 18 are set at a thickness of about 0.2 mm. The conductive layer 16 is set at a thickness of about 500 xc3x85. The first and second transparent substrates 9, 14 are set at a thickness of about 0.7 mm. The black matrix 12 is set at a thickness of about 1 xcexcm. The color layer 13 is set at a thickness of about 1 xcexcm. The smoothing layer 15 is set at a thickness of about 1 xcexcm. The orientation film 11 is set at a thickness of about 500 xc3x85. The data line 5 and the pixel electrode 2 are set at a thickness of about 2000 xc3x85. The layer-to-layer insulation film (gate insulation film) 10 is set at a thickness of about 5000 xc3x85. The passivation film 22 is set at a thickness of about 3000 xc3x85. The common electrode 4 is set at a thickness of about 5000 xc3x85.
FIG. 3 shows a second plan view according to the conventional display cell. A display cell 202 shown in FIG. 2 is provided with an amorphous silicon 1, a pixel electrode 2, a gate electrode 3, a common electrode 4, a data line 5, a source electrode 6 and a drain electrode 7.
FIG. 4 shows a section of the cell 202. FIG. 4 shows a second section according to the conventional display cell. In FIG. 4, the upper structure located on an upper portion of a liquid crystal layer in which a liquid crystal 20 is placed is provided with a polarization plate 17, a conductive layer 16, a second transparent substrate 14, a black matrix 12, a color layer 13, a smoothing film 15 and an orientation film 11.
In FIG. 4, the lower structure located on the lower portion of the liquid crystal layer is provided with an orientation film 11, a passivation film 22, a data line 5, a pixel electrode 2, a layer-to-layer insulation film (gate insulation film) 10, a common electrode 4, a first transparent substrate 9 and a polarization plate 18.
The display cell 202 shown in FIGS. 3, 4 differ from the cell 201 shown in FIGS. 1, 2 in the shapes of the edges of the pixel electrode 2 and the common electrode 4. The other configurations are same. Due to the difference between the shapes, there is no region where the liquid crystal is inversely rotated in the vicinity of the edge in the display cell 202. Thus, it is possible to improve the display performance and the reliability.
FIG. 5 is a view showing a first drive performance of the IPS liquid crystal display apparatus. As shown in FIG. 5, the IPS liquid crystal display apparatus is designed such that when an interval between the comb electrodes (an interval between the pixel electrode 2 and the common electrode 4) is made narrow, the liquid crystal can be driven at a low voltage. However, on the other hand, the narrower interval between the electrodes increases the areas of the common electrode and the pixel electrode which are opaque. Thus, this results in a problem that a brightness is reduced because of a drop in an aperture ratio.
FIG. 6 is a view showing a second drive performance of the IPS liquid crystal display apparatus. As shown in FIG. 6, a responsive speed is made shorter if a cell gap is made narrower (the interval between the color filter substrate and the substrate with TFT: the thickness of the liquid crystal layer). However, on the other hand, there is a problem that if the cell gap is made narrower, a predetermined brightness can not be obtained unless a voltage to drive the liquid crystal is made higher.
FIG. 7 is a view showing the drive concept in the vicinity of the comb electrode in the IPS liquid crystal display apparatus. As shown in FIG. 7, the liquid crystals 20 are oriented along the electric field generated by the actions of the pixel electrode 2 and the common electrode 4 (in a direction vertical to an equi-potential surface 61). Also, the orientation directions of the liquid crystals are different on a right half and a left half on the pixel electrode 2, with a center of an electrode width as an axis. Thus, a discrimination is induced (a discrimination occurrence position 62). Hence, a light shield function is required for the discrimination occurrence position 62.
Japanese Laid Open Patent Application (JP-A-2000-39625) discloses a liquid crystal display apparatus for making light transparent ratio high and preventing inconsistencies in display from occurring.
In the IPS liquid crystal display apparatus, the drop in a viscosity of liquid crystal material and the narrow cell gap must be essentially attained in order to make the responsive speed faster. The improvement of the responsive speed using this method has the problem involving the increase in the drive voltage, as shown in FIG. 6. Thus, it is necessary to make the interval between the comb electrodes narrower, in order to set this drive voltage, for example, to be equal to or less than 5 V and also obtain a desirable strength of an electric field. However, if the interval between the comb electrodes is made narrower, since the pixel electrode and the common electrode are opaque, the aperture ratio is dropped, and the brightness is reduced. Hence, it is virtually impossible to make the interval between the comb electrodes narrower, and thereby obtain the desirable strength of the electric field.
The present invention is accomplished in view of the above mentioned problems. Therefore, an object of the present invention is to provide an active matrix type of a liquid crystal display apparatus which can keep a desirable aperture ratio, drive a liquid crystal at a low voltage, and improve a responsive speed and further protect a coloration from an oblique field.
In order to achieve an aspect of the present invention, an active matrix type of a liquid crystal display apparatus, includes: a pair of substrates; a liquid crystal layer provided between the pair of substrates; a pixel electrode and a common electrode provided on at least one side of the pair of substrates, wherein the pixel electrode and the common electrode are provided at established intervals to be shaped like teeth of a comb to generate an electric field substantially parallel to the pair of substrates in the liquid crystal layer; and a transparent auxiliary electrode provided through an insulating film above the common electrode, wherein a same voltage as that of the common electrode is applied to the transparent auxiliary electrode such that the electric field applied to the liquid crystal layer is strengthened.
In order to achieve another aspect of the present invention, an active matrix type of a liquid crystal display apparatus, includes: a pair of substrates; a liquid crystal layer provided between the pair of substrates; a pixel electrode and a common electrode provided on at least one side of the pair of substrates, wherein the pixel electrode and the common electrode are provided at established intervals to be shaped like teeth of a comb to generate an electric field substantially parallel to the pair of substrates in the liquid crystal layer; a first transparent auxiliary electrode provided above the pixel electrode; and a second transparent auxiliary electrode provided above the common electrode through a contact hole electrically connected to the first transparent auxiliary electrode, and wherein the first transparent auxiliary electrode is formed on a same layer as that on which the second transparent auxiliary electrode is formed.
In order to achieve still another aspect of the present invention, an active matrix type of a liquid crystal display apparatus, includes: a pair of substrates; a liquid crystal layer provided between the pair of substrates; a pixel electrode and a common electrode provided on at least one side of the pair of substrates, wherein the pixel electrode and the common electrode are provided at established intervals to be shaped like teeth of a comb to generate an electric field substantially parallel to the pair of substrates in the liquid crystal layer; a first transparent auxiliary electrode provided above the pixel electrode; and a second transparent auxiliary electrode provided above the common electrode through a contact hole electrically connected to the first transparent auxiliary electrode, and wherein the first transparent auxiliary electrode is formed on a first layer and the second transparent auxiliary electrode is formed through an insulating film on a second layer different from the first layer.
In order to achieve yet still another aspect of the present invention, an active matrix type of a liquid crystal display apparatus, includes: a pair of substrates; a liquid crystal layer provided between the pair of substrates; a pixel electrode and a common electrode provided on at least one side of the pair of substrates, wherein the pixel electrode and the common electrode are provided at established intervals to be shaped like teeth of a comb to generate an electric field substantially parallel to the pair of substrates in the liquid crystal layer; and a transparent auxiliary electrode provided through an insulating film above a single one of the pixel electrode and the common electrode, wherein the transparent auxiliary electrode is electrically connected to the single one through a contact hole.
In this case, the liquid crystal display apparatus includes a plurality of the contact holes per a display pixel of the liquid crystal display apparatus.
Also in this case, the liquid crystal display apparatus includes a plurality of the contact holes per a display pixel of the liquid crystal display apparatus.
Further in this case, the liquid crystal display apparatus includes a plurality of the contact holes per a display pixel of the liquid crystal display apparatus.
In this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein each of the pixel electrode and the common electrode and the transparent auxiliary electrode is shaped like a straight line.
Also in this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein each of the pixel electrode and the common electrode and the transparent auxiliary electrode is shaped like a straight line.
Further in this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein each of the pixel electrode and the common electrode and the transparent auxiliary electrode is shaped like a straight line.
In this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein each of the pixel electrode and the common electrode and the transparent auxiliary electrode is shaped like a straight line.
Also in this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein at least one of the pixel electrode and the common electrode and the transparent auxiliary electrode is shaped like bent.
Further in this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein at least one of the pixel electrode and the common electrode and the transparent auxiliary electrode is shaped like bent.
In this case, the at least one of the pixel electrode and the common electrode and the transparent auxiliary electrode is created in a form of a triangular notch.
Also in this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein a width of the transparent auxiliary electrode is wider than those of the pixel electrode and the common electrode such that a space between the teeth of the comb is lessened.
Further in this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein a width of the transparent auxiliary electrode is wider than those of the pixel electrode and the common electrode such that a space between the teeth of the comb is lessened.
In this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein a width of the transparent auxiliary electrode is wider than those of the pixel electrode and the common electrode such that a space between the teeth of the comb is lessened.
Also in this case, the pixel electrode and the common electrode and the transparent auxiliary electrode are shaped like teeth of the comb to generate the electric field, and wherein a width of the transparent auxiliary electrode is wider than those of the pixel electrode and the common electrode such that a space between the teeth of the comb is lessened.
Further in this case, a center line of a width of the transparent auxiliary electrode is a same as that of one of the pixel electrode and the common electrode.
In this case, a material of the transparent auxiliary electrode is an ITO.